Trump calls troops, congratulates himself

President Donald Trump used a Thanksgiving Day call to troops deployed overseas to pat himself on the back and air grievances about the courts, trade and migrants heading to the US-Mexico border.

Trump's call, made from his opulent private Mar-a-Lago club, struck an unusually political tone as he spoke with members of all five branches of the military to wish them happy holidays.

"It's a disgrace," Trump said of judges who have blocked his attempts to overhaul US immigration law, as he linked his efforts to secure the border with military missions overseas.

Trump later threatened to close the US border with Mexico for an undisclosed period of time if his administration determines Mexico has lost "control" on its side.

Two little girls who are part of a migrant caravan share a sandwich in Tijuana, Mexico. (AAP)

The call was a uniquely Trump blend of boasting, peppered questions and off-the-cuff observations as his comments veered from venting about slights to praising troops - "You really are our heroes," he said - as club waiters worked to set Thanksgiving dinner tables on the outdoor terrace behind him.

And it was yet another show of how Trump has dramatically transformed the presidency, erasing the traditional divisions between domestic policy and military matters and efforts to keep the troops clear of politics.

"You probably see over the news what's happening on our southern border," Trump told one Air Force brigadier general stationed at Bagram Airfield in Afghanistan, adding: "I don't have to even ask you. I know what you want to do, you want to make sure that you know who we're letting in."

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Later, Trump asked a US Coast Guard commander about trade, which he noted was "a very big subject" for him personally.

A member of the migrant caravan sits atop the border wall between the United States and Mexico. (AAP)

"We've been taken advantage of for many, many years by bad trade deals," Trump told the commander, who sheepishly replied that, "We don't see any issues in terms of trade right now."

And throughout, Trump was sure to congratulate himself, telling the officers that the country is doing exceptionally well on his watch.

"I hope that you'll take solace in knowing that all of the American families you hold so close to your heart are all doing well," he said. "The nation's doing well economically, better than anybody in the world." He later told reporters "nobody's done more for the military than me."

Indeed, asked what he was thankful for this Thanksgiving, Trump cited his "great family," as well as himself.

"I made a tremendous difference in this country," he said.

President Donald Trump waves as he leaves the room following his talk with reporters and troops via teleconference from his Mar-a-Lago estate in Palm Beach, Florida. (AAP)

Trump later travelled to a nearby Coast Guard station, where he delivered a lunch of plastic-wrapped sandwiches, fruit and chips before spending some time at one of his golf courses.

He and his family capped the day with several hundred dues-paying members and their guests at a Thanksgiving feast in Mar-a-Lago's opulent ballroom that included the usual fixings, along with chilled seafood, Chilean sea bass and braised short ribs.

US Customs and Border officials speak to a caravan member at the San Ysidro port of entry between Tijuana and San Diego. (AAP)